#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct _node {
    int item;
    struct _node *next;
} node;

typedef struct {
    node *front;
    node *back;
} queue;

queue initq ()
{
    return (queue){NULL, NULL};
}

int isempty ( queue Q )
{
    return (Q.back == NULL);
}

queue enq ( queue Q, int x )
{
    node *p;
    
    p = (node *)malloc(sizeof(node));
    p -> item = x;
    p -> next = NULL;
    if (isempty(Q)) {
        return (queue){p, p};
    }
    Q.back -> next = p;
    Q.back = p;
    return Q;
}

int front ( queue Q )
{
    if (isempty(Q)) return -1;
    return Q.front -> item;
}

queue deq ( queue Q )
{
    node *p;
    
    if (isempty(Q)) return Q;
    p = Q.front;
    Q.front = Q.front -> next;
    if (Q.front == NULL) Q.back = NULL;
    free(p);
    return Q;
}

int main ()
{
    char A[128] = "abcdefghijklmnopqrstuvwxyz", f;
    queue Q;
    int i, j, alen;
    
    Q = initq();
    alen = strlen(A);
    for (i=0; i<alen; ++i) Q = enq(Q, (int)A[i]);
    for (j=0; j<alen; ++j) {
        for (i=0; i<alen; ++i) {
            f = (char)front(Q);
            printf("%c",f);
            Q = deq(Q);
            Q = enq(Q,f);
        }
        printf("\n");
        f = front(Q);
        Q = deq(Q);
        Q = enq(Q,f);
    }
    return 0;
}